To investigate the relationships between the levels of interleukin-4 (IL-4), interleukin-6 (IL-6) and interferon-γ (IFN-γ) of bronchoalveolar lavage fluid (BALF) and the disease condition and pulmonary function in children with Mycoplasma pneumoniae pneumonia (MPP).

Total of 109 cases with MPP (study group) and 102 cases of acute bronchial foreign bodies (control group) in Xuzhou Children’s Hospital Affiliated to Xuzhou Medical University from May 2019 to October 2020 were enrolled. The patients in study group were divided into mild disease group (85 cases) and severe disease group (24 cases) according to the conditions; and divided into normal lung function group (26 cases), mild lung function injury group (32 cases), moderate lung function injury group (30 cases) and severe lung function injury group (21 cases) according to the degree of lung function injury. The levels of IL-4, IL-6 and IFN-γ of BALF among all cases were detected by enzyme-linked immunosorbent assay (ELISA). The levels of IL-4, IL-6 and IFN-γ of BALF were compared among cases with different conditions and different grades of lung function injury. The above indexes were compared between two groups by t-test for group design data; multi-group overall comparison were taked by ANOVA, and pairwise comparison were analyzed by LSD-t test. The correlations between the levels of IL-4, IL-6, IFN-γ of BALF and lung function were analyzed by Pearson correlation-analysis.

The levels of IL-4, IL-6 and IFN-γ of BALF of cases in study group were significantly higher than those of control group [IL-4: (142.4 ± 24.7) pg/ml vs. (73.2 ± 13.0) pg/ml: t = 25.159, P < 0.001; IL-6: (56.4 ± 10.3) pg/ml vs. (11.2 ± 2.3) pg/ml: t = 43.399, P < 0.001; IFN-γ: (90.2 ± 16.3) pg/ml vs. (41.8 ± 6.8) pg/ml: t = 27.857, P < 0.001]. The levels of IL-4, IL-6 and IFN-γ of BALF of children in severe injury group were (200.7 ± 36.7) pg/ml, (103.3 ± 16.8) pg/ml and (113.5 ± 21.9) pg/ml, which were significantly higher than those of mild disease group [(125.9 ± 22.4) pg/ml, (43.1 ± 7.8) pg/ml and (83.6 ±14.1) pg/ml], with significant difference (t = 12.378, P < 0.001; t = 25.010, P < 0.001; t = 8.035, P < 0.001). The levels of IL-4, IL-6 and IFN-γ of BALF in children with normal lung function were (81.6 ± 15.5) pg/ml, (20.4 ± 4.2) pg/ml, (74.7 ± 11.9) pg/ml, and (102.5 ± 19.9) pg/ml, (48.9 ± 8.2) pg/ml, (89.2 ± 11.1) pg/ml in mild lung function injury group, and (145.7 ± 25.2) pg/ml, (60.2 ± 10.2) pg/ml, (95.4 ± 12.8) pg/ml in moderate lung function injury group, and (273.7 ± 42.1) pg/ml, (106.9 ± 17.6) pg/ml, (103.2 ± 13.2) pg/ml in severe lung function injury group, respectively. The levels of IL-4, IL-6 and IFN-γ in BALF of cases in mild, moderate and severe lung injury groups were significantly higher than those of normal lung function group (all P < 0.05), the levels of the above three indexes of cases in moderate, severe lung injury function group were significantly higher than those of mild lung injury group (all P < 0.05), and those of severe lung injury group were significantly higher than those of moderate lung injury group (IL-4: t = 13.581, P < 0.001; IL-6: t = 11.956, P < 0.001; IFN-γ: t = 2.117, P = 0.039), all with significant differences. The levels of IL-4, IL-6 and IFN-γ of BALF in study group were negatively correlated with forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), peak expiratory flow (PEF) (IL-4 with FEV₁, FEV₁/FVC and PEF: r =-0.834, P = 0.025; r =-0.810, P = 0.009; r =-0.901, P = 0.002; IL-6 with FEV₁, FEV₁/FVC and PEF: r =-0.816, P = 0.003; r =-0.795, P = 0.012; r =-0.743, P = 0.007; IFN-γ with FEV₁, FEV₁/FVC and PEF: r =-0.756, P = 0.012; r =-0.738, P = 0.010; r =-0.725, P = 0.017).

The levels of IL-4, IL-6 and IFN-γ of BALF were increased in children with MPP, which were correlated with the disease conditions and lung function.